Abstract: Based on analysis of reservoir characteristics of drilled well and successful experience of stu-dying string beads anomaly reflection on karst-fracture-cavity type reservoirs in Tahe oilfield,passelkaYSt-fracture-cavity type reservoirs had been discovered in the study area.The discovery was resul-ted from the forward modeling of karst-fracture-cavity type reservoirs,combining time slice of rootmean square amplitude,change rate of amplitude and seismic time migration section.The string beadsanomaly reflection was also classified and appraised by depicting the present structure and paleogeomor-phic characteristics and so on.